A Three-dimensional Thermal Model Of Lithium-ion Batteries And Its Application

Faced with the pressure of the environment and energy, the electric vehicle technology is now the most promising technical solution for major auto companies and institutions. And one of the hotspot is the battery safety. In recent years, with the characters of large capacity and long cycling life, lithium batteries becomes the best power sources choice for electric vehicles. Therefore, the thermal safety of lithium battery becomes the object of attention.In this research, the basic battery tests of three kinds of lithium batteries, which were the same capacity(35A ? h) but with different cathode materials(LMO, ternary material, LMO ternary hybrid materials) were carried out to get the charge or discharge curves and temperature curves. Then, short circuit, overcharge, high temperature and nail test were carried out on the three lithium batteries to get its temperature curves by thermocouples.A three-dimensional thermal model was developed by COMSOL. Then, its reliability and accuracy were verified by comparison. Simulation was applied by the models of the three lithium batteries under the short circuit, high temperature and nail test conditions, and the safety performances were deeply compared. Under the short circuit condition, the LMO battery reached the highest temperature and the ternary material battery got the lowest, but the gap was not obvious. Under the high temperature condition, the performance was almost the same for these batteries. And under the nail test condition, the ternary material battery got a really high temperature more than 1600 K and the LMO battery showed no difference.The model was also simulated under the high temperature condition for 140, 150 and 160℃. Through the comparison of the temperature curves and analysis of the side reactions, we knew that 150℃ is the temperature which the lithium batteries will generate a lot of heat.The arrangement of lithium battery pole ears were studied. Different arrangements were compared by the simulation of the lithium battery under the high temperature condition. The research showed that the pole ears arranged on the two narrow edges was better for the thermal safety.